1. Field of the Invention
The present invention relates to a heating element which uses heat generated upon the application of current to charcoal and, at the same time, can absorb gas.
2. Background Art
Heating elements using heat generated upon the application of current to carbon are widely known. For example, Japanese Patent Laid-Open No. 258842/1993 discloses a resistance heating element prepared by dispersing carbon fibers in Japanese paper washi to form a planar heating element. Japanese Patent Laid-Open No. 190873/1997 discloses a heating element prepared by mixing graphite powder with resin and coating the mixture onto a substrate. Japanese Patent Laid-Open No. 354257/1999 discloses a carbon heating element in a hollow form. This heating element is prepared by mixing graphite, resin, and a ceramic together, molding the mixture, treating the molded product at a temperature of 800° C. or above in an inert gas, and further baking the treated molded product in vacuo at a temperature of 1200° C.
On the other hand, a sick building syndrome or a sick house syndrome and chemical sensitivity have recently become a problem. These diseases may be caused by chemical substances released from construction materials or the like in highly airtight buildings. Studies have been made on uptake of such chemical substances present in the room by charcoal through the utilization of absorptive capacity of the charcoal to inhibit the occurrence of these symptoms.
Specifically, a proposal has hitherto been made on a technique in which a wood charcoal or a bamboo charcoal is ground to a charcoal powder and the powder is mixed with various materials to prepare a building material (for example, Japanese Patent Laid-Open Nos. 150645/1995 and 49916/1994).
Further, Japanese Patent Laid-Open No. 226207/2000 discloses a production process of an activated wood charcoal having both a low-temperature carbonized part and a high-temperature carbonized part. This production process comprises the steps of: heat-treating wood chips at 450 to 550° C. to carbonize the wood chips (a low-temperature carbonization step); and subsequently heat-treating the carbonized wood chips at 800 to 900° C. to further carbonize the wood chips (a high-temperature carbonization step). In this publication, however, there is no specific disclosure on any molded product using this activated wood charcoal. Further, this publication neither suggests nor discloses any useful binder for molding.